The general field of this invention is a method and apparatus for a simultaneous, rotary process, high throughput capacity manufacturing of single-component and dual-component fibres from thermoplastic materials, and thermal and acoustical insulation products formed from a certain mixture of such fibres. More particularly, this invention relates to a method and apparatus for the combined centrifuging single-component, straight and dual-component, curly glass fibres, and products formed from these straight and curly glass wool type fibres.
A typical glass fibre thermal or acoustical insulation product is made of rather short, single glass and basically straight glass fibres. A common method of manufacturing these glass wool type fibres is a rotary fiberizing process, where a single molten glass composition is forced by a high speed rotation through the orifices in the peripheral wall of a centrifuge, usually referred to as a spinner, and is further subjected to the combined action of a high temperature flame and low temperature/high velocity compressed air blasts.
It has been recognized that virtually straight fibre geometry, offered by a conventional rotary fiberizing process, certainly is not the best one for forming some high performance thermal and acoustical insulation product. It became apparent that adding an element of curvature to the basic fibre shape should, in principle, offer some highly desired and sought for features and product attributes, including a substantially higher allowable product compression ratio, therefor offering quite substantial cost savings in product storage, transportation (distribution) and also in packaging materials. Other advantages are a better volume filling ability, lower dust level, less itch, and potential for much lower organic binder level required to assure product integrity. This is due to the improved curly fibre self-cohesion, interlocking and intertwining properties. The result is lower binder cost, and reduced organic emissions. It is also reasonable to expect a slightly higher product thermal resistance, i.e., a possibility of increased earnings due to consequential density reductions.
The very first attempts to make curly glass fibre were based on a differential cooling, quenching or the like of a textile-type single glass composition fibre (U.S. Pat. No. 2,927,621). Both the fibre and process were not suitable for insulation products. Tiede in U.S. Pat. No. 3,073,005 discloses a non-rotary fiberizing process for making bi-component curly glass fibre. Two glasses with differing thermal expansion coefficients are put into side by side contact. This bi-component curly fibre was not meant to be used for insulation products. Some other patents disclosing methods of making curly or kinky glas fibres are disclosed in U.S. Pat. Nos. 3,236,616 and 4,145,199, but sill these methods would not be that practical for making an insulation product.
It is generally accepted that a non-rotary fibre-forming process cannot effectively compete with the rotary one for the economic manufacture of a typical glass fibre-insulating product. The issues are a substantially lower throughput capacity and too coarse fibre to make a good glass wool. As a consequence, some methods of imparting kink by pulling fibre from a textile bushing and mechanically crimping it by passing fibre, while still in a hot state, through a series of opposed intermeshing gears are not a viable option.
In the early 1960's, Stalego (U.S. Pat. No. 2,998,620) disclosed a rotary method for making a bi-component curly glass fibre, where two glass compositions differ in their thermal expansion coefficients, however, there is no mention of using these curly fibres for insulation products. In the mid 1990's, Owens-Corning obtained the first patents for protecting a newly developed technology for manufacturing bi-component curly glass fibre by a rotary fiberizing technique, with the clear objective of using this non-straight or irregular dual-glass fibre for thermal and acoustical insulation products. The scope of patenting is wide, including both processes, apparatus and product. By 2002, other major or global manufacturers of fibre glass insulation, namely Isover Saint Gobain and Johns-Manville, were granted patents for manufacturing dual-glass curly wool type fibres.
A typical approach to manufacture curly bi-component glass fibre by rotary fiberizing, is to use two glass formulations with widely different coefficients of thermal expansion and feed these two glasses as separate glass streams, in a radially displaced configuration, into some sort of integrated glass distributor inside a spinner assembly and force first and second glasses into alternate vertical compartments circumferentially spaced around the interior of the spinner peripheral wall. Finally, one centrifuges these two glasses through orifices drilled in the spinner peripheral wall along the adjacent compartments dividing line in such a way that the two glasses join each other in a side-to-side contact before emerging from a single orifice as a bi-component fibre.
Some spinner designs for making dual-glass curly fibres are disclosed in U.S. Pat. Nos. 5,468,275; 5,474,590; 5,595,766; and 5,987,928. Clearly, a throughput capacity offered by these dual-glass spinners cannot be reasonably high, making the whole operation rather costly.
A binderless, plastic sleeve encapsulated, extremely high compression ratio insulation product, entirely formed from rotary process which made dual-glass curly fibre, became commercially available in the early 1990's. Since the product had no binder, an irregularly-shaped glass fibre, after being collected at approximately 600 degrees Celsius temperature on opposed, downwardly converging collection conveyors, were passed through a heat-setting oven to shape the individual fibres into a cohesive insulation product at temperatures from approximately 400 to 600 degrees Celsius.
There are numerous patents disclosing both the method of manufacturing (process) and dual-glass fibre insulation products, for example, the following U.S. Pat. Nos.: 5,431,992; 5,536,550; 5,618,327; 5,629,089; 5,672,429; and 5,723,216. Insulation products comprised of irregularly-shaped glass fibres exhibit a substantially uniform volume filling nature, and provide improved thickness recovery and thermal insulating abilities.
Irregularly-shaped dual-glass fibres for pourable or blowable loose-fill insulation products (blowing wool) are disclosed in U.S. Pat. Nos. 5,624,742; 5,683,810; and 5,786,082. Some benefits include improved coverage (lower product densities), higher thermal efficiency and less dust upon blowing or pouring. A loose-fill insulation product can entirely be made of irregularly-shaped dual-glass fibres, or be some blend of single-glass and dual-glass fibres.
A need exists for an improved glass wool insulating material. Of particular importance is a substantially higher product thickness recovery (allowable compression ratio) and reduced thermal conductivity. The product should be made in a cost effective way, meaning production rates closely matching the existing ones, and the overall process changes kept to the absolute minimum. It is believed that insulation material made as some mixture or blend of single-glass straight, and dual-glass curly fibres, simultaneously fiberized by the same spinner, mixed right during the fibre-forming stage, bonded by a 20 percent to 50 percent reduced amount of standard, phenol-formaldehyde binder, and further processed in a standard or conventional way, should in principle meet expectations. No use of an encapsulating plastic sleeve should be necessary. The insulation product should be suitable for all typical applications. Skin irritation and material dustiness, factors particularly important to product end users or installers, should be reduced.
U.S. Pat. No. 5,968,645 discloses an insulation product made as a mixture of single-component and multi-component inorganic fibres, where the material cohesion and shape is ensured, at least partially, by using some sort of organic or inorganic binder. Such product exhibits a remarkable recovery of thickness after decompression. Being compressed to 1/20th of its initial thickness for 72 hours, the product bounces back to 110 percent to 120 percent of its nominal thickness, the thickness required during product installation after unpacking. This 20:1 compression ratio favourably compares with a typical 10:1, allowable ratio for a standard, single-component light density fibreglass insulation products. For a given product density, its thermal insulation performance is slightly better as well. Unlike a binderless, plastic sleeve enclosed or encapsulated insulating material, consisting only of bi-component irregularly-shaped glass fibres, this product lends itself to thermal or acoustical insulation of vertical walls in buildings.
Canadian Patent Application CA 2202208 describes a method and device for producing mineral wool products being in principle a mixture of four distinct types of glass fibres, namely a straight single-glass fibres of glasses A and B, curly dual-glass fibre where there is a mutual side-to-side contact along the entire fibre length, and a composite or compound curly fibre where two single-glass fibres are joined at separate points only along the compound fibre length, resulting in a twisted or curled rope ladder fibre structure. The spinner design is based on having separate and alternate vertical glass compartments and two chambers for glasses A and B along the spinner circumferential wall. By adding single-glass orifices to a dual-glass spinner structure, a substantial increase in productivity can be achieved. This modified spinner follows the basic design explained in U.S. Pat. No. 5,987,928.
Thermal and mechanical properties of such insulation product can be controlled and optimized. There is a wide field of possible combinations and/or mixtures of pure mono-composition straight fibres, composite curly fibres and bi-component irregularly-shaped fibres to choose from. Softer glass will work as a binder, at least in certain cases. There is no direct mention of using standard organic binder for this mixed fibre insulation product made by a rotary fiberizing technique.
European Patent Application EPO 994079 discloses a method and apparatus for manufacturing an insulation product consisting of single-glass straight and dual-glass curly fibres. It discloses a dual-glass spinner with separate vertical glass compartments for glasses A and B, arranged in an alternate fashion along the inner side of the spinner circumferential wall, is additionally equipped with a multiplicity of single-glass bores drilled in the spinner peripheral wall in the central area of any vertical glass compartment. A substantial spinner throughput capacity increase will result. The thermal and/or acoustical insulation product is a mixture of straight single-glass fibres of glass A, glass B and dual-glass curly fibres. It is claimed to be a binderless product. Thermal, and particularly mechanical properties of the insulation product are expected to be substantially improved.